EAPSI: Soil microbes and stream health: the effect of nutrient load on soil nitrogen removal capacity

Tatariw Corianne, Orono ME

Investigators

Abstract

Humans have dramatically increased the amount of reactive nitrogen in the environment with negative ecological consequences. Bacteria that live in soil and water have the ability to permanently remove excess nitrogen through a process called denitrification. Runoff from dairy farms is the main source of excess nitrogen in New Zealand waters, and has negative impacts on mahinga kai, freshwater species that are a traditional food source for the Māori. However, dairy export is an important part of the New Zealand economy. Therefore, it is important to understand the capacity of bacteria to remove nitrogen (N) in soils and streams to define limits on nitrogen application rates that protect the environment. The objective of this study is to relate changes in microbial community composition and soil conditions to denitrification rates in New Zealand dairy pasture soils and adjacent streams. This research will be conducted in collaboration with Dr. Gavin Lear, an expert in microbial ecology, at the University of Auckland in New Zealand. Denitrification hotspots in riparian soils will be predicted by relating denitrifier abundance (quantitative polymerase chain reactions of functional genes), microbial community structure (automated ribosomal intergenic spacer analysis), and soil conditions to denitrification rates. In order to better understand the factors regulating denitrification under different N-loading regimens, this study will be replicated in the United States on an experimental watershed subjected to 24 years of atmospheric N deposition at Bear Brook Watershed in Maine. This comparison study is novel because it differentiates between N loading route and land-use effects when assessing factors that influence denitrification rates. This research will clarify the relationship between microbial diversity and ecosystem functioning at local and global scales through its spatially structured design. This NSF EAPSI award is funded in collaboration with the Royal Society of New Zealand.